Field of the Invention
The present invention relates to a disc for disintegrating a solid wood block to produce fibrous strands or elements for use in making composites. In particular, the present invention relates to a disc which has teeth formed in rows which contact the wood block to shred the wood block to produce fibrous elements. The disc is also provided with a scraper which completely detaches fibrous elements from the wood block. The wood block is fed into the disc such that the teeth of the disc strike the wood block in a circular path along the preferred grain direction of the wood block.
In the lexicon of the smaller wood elements derivable from wood, the terms: flake, strand, splinter, sliver, fiberbundle and fiber are associated with definite products into which they are composed. Each element contributes characteristics to the composite and to its processing in accordance with the element's geometry. The fibrous strand or fibrous element is a combination element being composed of both a strand-like element and fiber-like elements. The strand part may be straight but is usually bent or curved. The fibrous parts are partially cleaved appendages that branch off in random directions from the strand part.
Fibrous strands, like other wood elements, can be produced and have utility over a wide range of sizes. Fibrous strands are three-dimensional particles, compared to two-dimensional flakes, and one-dimensional slivers or splinters. Strands (actually narrow flakes) as used in Oriented Strand Boards (OSB) are strictly speaking, two-dimensional but are used in a one-dimensional manner (oriented) to create strength in a given direction.
The three-dimensional configuration of the fibrous strand contributes uniquely to its further processing and to the properties of the resulting composite material. Unlike flakes and other linear or flat elements that depose themselves parallel to the surface upon which they fall, fibrous strands assume a more random orientation. Thus, flakes contribute strength primarily in the x-y plane, leaving the z plane relatively weak. Fibrous strands, however, because of their more random orientation, produce substantially greater strength in the z planes. The z plane figures heavily in the performance of overlays and in the general integrity of the composite material.
Fibrous strands also compose themselves into a rather open but cohesive mat. Such a mat is easy to transport between operations, is easily infused with gases, liquids and powders, has less edge defects in pressing, produces strength perpendicular to faces, (high internal bond) and allows low, as well as high density composite materials to be made.
The three-dimensional configuration of fibrous strands confers versatility in consolidation to many types of products. Flat, molded or post-formed commodities or consumer products can be made, sometimes with the same composition. Properties are related to density which can range from about 8 pounds per cubic foot upward, depending upon the pressure applied during consolidation.
Fibrous strands can be produced either by impact milling or by shredding directly from stove-wood size blocks. Both methods produce suitable fibrous strands. One method of impact milling is described in Applicant's co-pending application entitled "Controlled Impact Comminution of Wood". This type of milling necessitates some prior preparation of the wood such as maxi-chipping, crushing, steaming or conditioning to appropriate moisture content.
In contrast, the shredding of stove-wood size blocks as described in the present application requires only chain-sawing to block size and perhaps some splitting to fit the feed opening of the apparatus. The block is held against an arrangement of teeth that are driven ever the face of the wood in a manner that partly shears and partly tears out the fibrous strands. Since the separating forces acting on the parent wood block are more precisely controlled than in impact milling, the resulting wood element has more uniformity and more precise dimensions. For the same reason, wood elements of similar configuration can be produced using different species of wood, an advantage with variable resources.
(2) Description of the Related Art
The apparatus of the present invention is related mechanically and structurally to such equipment as disc flakers that produce flakes for flakeboard by knife action and disc chippers that produce chips also by knife action for further reduction to fibrous elements by attrition mills that provide rolling shear action.
The present invention produces fibrous strands directly from solid wood blocks without the intermediate step of first producing chips. By advancing a wood block in a controlled grain direction against a rotating disc studded with precisely configured and sequentially deployed teeth followed by a scraper action, fibrous strands are extracted from the parent wood block.
The related art has shown various types of discs having knives providing radially disposed knife action for disintegrating wood blocks to produce chips for further processing. Illustrative are U.S. Pat. No. 2,388,799 to Payzer et al; U.S. Pat. No. 2,655,319 to Johnson and U.S. Pat. No. 3,746,062 to Nystrom et al.
Payzer et al describes a wood chipper disc which has an annular series of elongated radial openings within which are mounted chipper blades for the purpose of cutting pulp chips from the end of logs by across-the-grain cutting action.
Nystrom et al shows a wood chipper disc which has a plurality of cutting element holders located adjacent a hole. The cutting element holders are arranged at a number of concentrical circular lines. A second disc is mounted spaced apart and behind the first disc to provide rigidity.
Johnson shows a wood chipper with knives routed in a radial fashion on the face of the disc. The invention uses a non-uniform knife bevel as a means of producing better paper-making chips from logs fed end-wise with the knives cutting across the end grain of the wood.
Also of interest are U.S. Pat. No. 2,537,570 to Bossert; U.S. Pat. No. 3,462,089 to Whitlow; and U.S. Pat. No. 4,122,236 to Holman. Bossert shows a pair of grinding discs which are arranged face to face. The grinding surface of the discs are provided with a plurality of recesses and pockets. The solid particles, to be ground, are trapped in the recesses and pockets of each disc. The solid particles of the material in the recesses and pockets of each disc are ground by the solid particles in the recesses and pockets of the other disc and are sheared by the knife-like edges of such recesses and pockets. Whitlow shows a disc for refining chips to a pulp slurry. The face plate of the disc is comprised of a plurality of arcuate segments. The segments include a plurality of upstanding, relatively radially short teeth in the form of ridges between which are disposed a plurality of upstanding, relatively radially long teeth in the form of ridges. Both teeth are provided with sharp edges. Holman shows the use of an across-the-grain picking action to produce splints from a log.
Only of minimal interest are U.S. Pat. No. 2,154,650 to Wishinsky; U.S. Pat. No. 3,489,356 to Combs et al and U.S. Pat. No. 4,660,778 to Fischer at al. Wishinsky shows a vegetable grater in the form of a rotating disc having scoring members and scraping blades. The scorers and blades are positioned in groups so that each group defines a quadrant of the disc with the blades in any group being parallel to a straight edge boundary of the quadrant they occupy and perpendicular to the blades in an adjoining quadrant. Combs et al describes an impeller for mounting in a slurry tank for pulping slurry solids. Fischer et al shows an impeller disc for use in size reducing a food product. The disc has a plurality of blades which are of the same length and which are alternately displaced upwardly and downwardly with the upwardly displaced blades having forwardly inclined product-engaging surfaces and the downwardly displaced blades having rearwardly inclined product-engaging surfaces.
There remains the need for an apparatus which can be used to produce fibrous strands or elements from solid wood blocks. The fiberizing disc of the present invention having a plurality of teeth mounted in several rows on the disc provides a means of producing fibrous elements from solid wood blocks. The positioning of the teeth on the disc and the direction of feed of the wood block allows the teeth on the disc to strike the wood block in a circular path along the preferred grain of the wood block. In addition, a scraper on the disc allows for completely detaching fibrous elements from the wood block. The construction of the disc allows the creation and extraction of fibrous elements from a solid wood block in a controllable manner.
OBJECTS
It is therefore an object of the present invention to provide a wood fiberizing disc which will produce fibrous elements from a wood block suitable for use in producing composite products. Further, it is an object of the present invention to provide a wood fiberizing disc which produces a variety of different forms of fibrous elements from solid wood blocks. Still further, it is an object of the present invention to provide a wood fiberizing disc having a plurality of teeth arranged such that each tooth functions relatively independently but cooperatively in forming and extracting fibrous elements from the wood block. Further still, it is an object of the present invention to provide a wood fiberizing disc which has a scraper for completely detaching fibrous elements from a wood block. Further still, it is an object of the present invention to provide a fiberizing disc which allows for inexpensive, easy, quick and controlled production of fibrous elements from wood blocks ultimately helping to address the problem of sustainability and biodiversity in forest resources by adding more value to low grade wood. It is further an object of the present invention to provide a means for the profitable utilization of wood unwanted or wasted because of species, size, form or distribution to thereby increase forest management options without decreasing the flow of forest products.
These and other objects will become increasingly apparent by reference to the following drawings and the description.